Semiconductor devices are used in a variety of electronic applications, such as personal computers, cell phones, digital cameras, and other electronic equipment, as examples. Semiconductor devices are typically fabricated by sequentially depositing insulating or dielectric layers, conductive layers, and semiconductive layers of material over a semiconductor substrate, and patterning the various material layers using lithography to form circuit components and elements thereon, forming an integrated circuit.
One type of semiconductor lithography involves positioning a patterned mask between a semiconductor workpiece and an energy source to expose portions of a photosensitive material deposited on the workpiece, transferring the mask pattern to the photosensitive material. The photosensitive material is then developed and used as a mask while exposed regions of a material on the workpiece are etched away. The photosensitive material is removed, and additional material layers are deposited and patterned in a similar fashion. There may be a dozen or more lithography mask levels required to manufacture an integrated circuit, for example.
Scanners are used in semiconductor device manufacturing to expose layers of photosensitive material. A portion, e.g., an exposure field, of a semiconductor workpiece is typically exposed at a time, and the scanner steps from one portion of the workpiece to the next, repeating the process until the entire workpiece is exposed.
As semiconductor devices are scaled down or reduced in size, lithography of semiconductor devices becomes more difficult. There are many parameters in a lithography system or process that may vary or shift, such as a focus level or exposure dose. The variations or shifts in these parameters may result in the formation of features on material layers of semiconductor devices that have undesired or unpredictable dimensions. Thus, it is desirable to detect variations of parameters such as focus level and dose in lithography systems or processes.
Therefore, what are needed in the art are improved methods and structures for testing lithography processes and systems, and test structures and methods for manufacturing semiconductor devices.